Solvent extraction process



June 17, 1941. w, u c ETAL 2,246,297

SOLVENT EXTRACTION PROCESS Filed Dec. 10, 1938 5 Sheets-Sheet l HARM/0N SOLVENT 1157- 15 I SOLVENT FEE 2: [N12 T p.

EXTRA CT I Sou/5N7 EPARATIQN I .S'cu. VENT 1941- G. w. DUNCAN ETAL 6, 97

SOLVENT EXTRACTION PROCESS Filed Dec. 10, 1958 3 Sheets-Sheet 2 I June 17, 1941. w, DUNCAN ETAL 2,246,297

SOLVENT EXTRACTION PROCE SS Filed Dec. -10, 1938 3 Sheets-Sheet 3 EXTRAC T LIA/E co/vTA C TIN zxrzn c7 scrum ER Patented June 17, 1

STATES PATENT OFFICE uh-2 Jr., Westfield, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application December 10, 1938, Serial No. 244,908

7 Claims.

The present invention relates to an improved process for the solvent treatment of mineral oils. The invention is particularly directed to the solvent treatment of lower boiling petroleum fractions with solvents of the class which have a preferential selectivity for the more aromatic type compounds as compared to the more parafflnic type compounds. In accordance with the process of the present invention petroleum oils boiling in the naphtha, kerosene and gas oil ranges are solvent treated with solvents of the class which are characterized by being completely miscible with toluene in the anhydrous state and very slightly miscible with toluene in the aqueous state at'ordinary temperatures and pressures. Suitable solvents of this class are, for example. ethylene and propylene glycols and their derivatives as well as certain esters of phosphoric acid and various amines. The present process utilizes solvents selected from this class in conjunction with water which is introduced into the treating system at more than one stage. The process of the present invention secures greater yields of higher quality products in an economical manner.

It is well known in the art to treat petroleum oils with various solvents in order to segregate the relatively more paraflinic constituents from the relatively more aromatic constituents. In these processes the mineral oil is contacted with a solvent at a temperature below that at which complete miscibility occurs. The solvent usually employed is selected from the class of solvents which have a preferential selectivity for the more aromatic type compounds as compared with the more paraflinic type compounds. Solvents of this class are, for example, phenol, furfural, sulfur dioxide, cresol, nitro benzene, aniline, beta beta dichlor diethyl ether and the like. Mixtures of these solvents are employed and are at times used in coniunction with other substances, as for example, substances of the class of liquefied normally gaseous hydrocarbons. The oil and the selective solvent are usually contacted in a countercurrent treating tower operation in which the heavier phase, usually the solvent, is introduced at the top of the countercurrent treating tower. The heavier phase flows downwardly through the tower intimately contacting the upfiowing lighter phase, usually the oil. A rafllnate phase rich in paraflinic type materials and containing a relatively small amount of the solvent is withdrawn from the top of the tower. The phase rich in nonparaflinic materials and containing the larger proportion of the solvent is withdrawn as the solvent extract phase from the lower part of the tower. Similar processes are also conducted by batch operations or by multi-batch operations. In these processes it is also known to use various substances, as for example, water, in conjunction with the selective solvent in order to modify or regulate the selectivity and solvent power of the particular solvent being used. The water may be contained in the solvent feed or may be injected at a point in the system. These solvents and processes while satisfactory in the solvent treatment of relatively high boiling petroleum oils, as for example, petroleum oils boiling in the lubricating oil range, have not been found entirely satisfactory for treating relatively low boiling hydrocarbons boiling in the naphtha, gas oil and kerosene range.

We have now discovered a process by which it is possible to solvent extract a relatively low boiling petroleum hydrocarbon oil with a solvent in an economical manner and to secure increased yields and higher quality products than have heretofore been possible. The process of our invention utilizes a solvent selected from the class of solvents which in the anhydrous state are entirely miscible with toluene in all proportions at ordinary working temperatures and which in the aqueous state are slightly miscible with toluene. The solvents of our invention are also characterized by the fact thatthey are more soluble in water than they are in toluene, and which may be readily extracted from toluene by washing with water. These characteristics of the solvent are essential for the successful operation of our invention and are met by relatively few substances. For example, phenol and furfural while completely miscible with toluene are more soluble in toluene than in water with the result that toluene will extract either phenol or furfural from dilute water solutions. In using solvents selected from this class in accordance with our process it is essential that they be used in conjunction with water which is introduced into the treating system at more than one stage.

The present process may be readily understood by reference to the attached drawings showing modifications of the same. Figure 1 is a diagrammatical sketch of a suitable countercurrent treating tower. Figure 2 is a diagrammatical sketch of a seven-stage countercurrent treater while Figure 3 illustrates a preferred procedure by which the solvent of the present invention may be recovered. Referring specifically to Figure 1, feed oil is introduced into the middle section of tower l by means of feed line 2. The 011 being the lighter component flows upwardly through tower I contacting downflowing solvent which is introduced into tower l by means of feed line 8. The solvent poor or rafllnate phase highly paraflinic in character is withdrawn by means of line 4, and introduced in rafflnate solvent separator l4. The separated solvent is withdrawn by means 01' line [5 and the solvent free rafflnate by means or line IS. The solvent rich phase highly non-parailinic in character is withdrawn as the solvent extract phase by means oi line 5 and introduced into solvent separator H. The separated solvent is removed by means of line l8 and the solvent free extract by means of line i9. Water is introduced into tower I, at two or more points, .by means of water inlet lines 6, I, 8 and 9 controlled by valves l8, ll, l2 and I3 respectively.

Referring specifically to Figure 2, feed oil is introduced into stage 48 by means of line 58. The raflinate phase is removed from stage 48 and introduced into stage 41 by means of line 28. In a similar manner the raflinate phases from stages 43, 44, 45, 41 and 48 are introduced into the next stage by means of lines 23, 24, 25, 21 and 28 respectively. The final raflinate phase containing a 49 by means of line 29 and subsequently treated to separate the solvent from the raflinate. The

extract phase from stage 45 is introduced into stage 45 by means of line 32. In a similar manner the extract phases from stages 44, 45, 41, 48 and 49 are introduced into the next stage by means of lines 38, 3!, 33, 34 and 35 respectively. The final extract phase containing the larger proportion of the solvent and highly non-parafiinic in character is withdrawn from sta e 43 by means oi. line 38 and treated to separate the solvent from the extract. It is to be understood that the solvent from either the ramnate or extract phase may be removed from the extract or rafflnate by the addition of further quantities of water. Water is injected into at least two stages by means of lines 31, 38, 39, 48, 4| and 42 Figure 3 illustrates a modification of the present invention as applied to a method of removing the-solvent without distilling. Feed oil is introduced into the central section of tower 58 by means of feed line 81. The oil flows upwardly through tower 68 intimately contacting downfiowing solvent which is introduced into the top of the tower by means of line 62. A rafllnate phase highly paramnlc in nature is withdrawn from tower 88 by means of line 63 and a solvent extract phase highly aromatic in nature is withdrawn from tower 88 by means of line 54. Water is injected into tower 88 at more than one stage by means of line 85 and lines 86, 61, 88, 69, I0 and II respectively. The solvent extract phase is introduced into mixer 12 in which it is contacted with sufficient water to substantially remove the solvent from the extract. The water may be introduced bv means of line 13 but is preferably introduced by means of line I4. The mixture is withdrawn from mixer 12 and introduced into settler 15 in which a phase separation occurs. The solvent water phase is removed from settler I5 and introduced into still 18 in which the water is separated from the solvent and removed by means of line I1. The solvent is removed from still I8 by means of line 18. The water removed by means of line I1 is introduced into condenser I9 and then led into water storage 88 from which it is recycled to the process by means of line 85. Some small quantities oi extract may separate in the upper layer of water storage 88 which may be introduced into the extract phase by means of line 8|. The extract separated from settler 1.5 is introduced into extract scrubber 82 by means oi line 88. In extract scrubber 82 the last traces of solvent are removed by countercurrent treatment with water introduced into the upper part of extract scrubber 82 by means of line 84. The solvent-free extract is removed from extract scrubber 82 by means of line 85. The water is removed from extract scrubber 82 by means of line 88 and introduced into rafllnate scrubber 81 in which it countercurrently scrubs the rafflnate phase which is introduced into the bottom of ramnate scrubber 81 by means oi! line 83. The solvent free ramnate is removed from rafflnate scrubber 81 by means or line 88 and the water by means of line 14.

As previously pointed out, the class of solvents with which the present invention is concerned are those solvents which in the anhydrous state are miscible with toluene in all proportions and which in the aqueous state are very slightly miscible with toluene at temperatures in the range from about 50 to F. The solvents of the present invention are those which may be readily removed from toluene by scrubbing with water. Solvent having these characteristics are, for example, glycols, derivatives of glycols, esters of phosphoric acid and amines. Suitable solvents are, for example, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, monomethyl ether of ethylene glycol, monomethyl ether oi! diethylene glycol, monomethyl ether of triethylene glycol, monoethyl ether of ethylene glycol, monoethyl ether oi. diethylene glycol, monoethyl ether of triethylene glycol, triethyl phosphate, tributyl phosphate, methyl amine, dlmethyl amine, ethyl amine and triethanol amine. Particularly desirable solvents in accordance with the process of the present invention are alkyl glycols and alkyl derivatives oi glycols having from one to two carbon atoms in the alkyl group, as for example, monomethyl ether 01 ethylene glycol, monoethyl ether of ethylene glycol, monomethyl ether of diethylene glycol and monoethyl ether of diethylene glycol. Especially desirable results are also secured when using alkyl esters of phosphoric acid made from methyl and ethyl alcohol, as for example, triethyl phosphate.

The volume of solvent used per volume of oil being treated will depend upon the particular petroleum 011 being treated, the solvent being used, the temperatures and pressures employed, as well as upon the yield and quality of products desired. In general. it is preferred to use from one-half to four volumes of solvent per volume of petroleum oil being treated. In general, it is preferred to use temperatures in the range from 60 to 100 F. and atmospheric pressure, although other temperature and pressure conditions may likewise be employed.

The solvent feed is preferably anhydrous and it is essential to introduce water into the system in at least two stages. Especially desirable operating results are secured when the water is introduced into the system in at least four stages, preferably at stages between the oil feed inlet and the raftlnate phase outlet and between the oil feed inlet and the extract phase outlet. The quantity ofwater addedwill depend upon the petroleum oil being treated, the solvent used and upon the treating conditions. The quantity of water introduced is preferably from about 5.0% to 20.0% of water based upon the total solvent used.

The invention is particularly adapted to the treatment of petroleum oils boiling in the range from about 100 F. to 650 F. Particularly desirable results are secured when extracting naphtha, especially those fractions boiling in the range from about 200 F. to 400 F.

In order to further illustrate the invention,

term. The results of the respective operations are summarized as follows:

TABLE 3 Percent wager E t t n so ven it me Opglration 32 3 regrac- Pereetnt ve aroma s solvent Above Below yleld index feed feed The tower was inoperable when less than 5.7%

of water was injected above the hydrocarbon the following examples are given which should feed point TABLE 4 not be construed as limiting the same in any manner whatsoever: Volumes EXAIIELE 1 Operation Operation Operation Various mixtures comprising 20 volumes of toluene, 20 volumes of water and 20 volumes of m. E particular solvents were made and the volume of Egg. 5: a 32?, 5. ,11%: the toluene layer and the water layer determined. The results of these tests were as fol- Amm t1 .o1efln 2&8 4&2 532 m8 lows: Saturated compounds .2 25.8 5.5 20.5 2.8 23.2 TABLE 1 26.0 74.0 49.0 56.0 44.0

volume volume of It is apparent from the above data that extoluene water tracts substantially free of saturated compounds layer may be readily prepared in accordance with the Acetone U 31 27 present invention. Ilcetonlyltacletrglneu.f..510] l... l 33 2g EXAIVIPLE 3 0110-113 6 eroe yenegyco Mono-butyl ether ofdi-ethylene giyeeL 40 20 35 A petroleum fraction having a gravity of about lmmmflhyl M 38 22 50 A. P. I. boiling in the range of about 200 F e yenegyco Acetate ester of mono-methyl ether of to 275 F. and containing about 75% aromatic ethylene glycfl 35 24 hydrocarbons was solvent treated with mono- The above data indicate that solvents of this class are not suitable since the solvent is not readily removed from toluene by means of water.

TABLE 2 TABLE 5 Extract Rafiinate Volume of Volume of Pewent Percent Percent refractive refractive Perm toluene water ation solvent water extract index at index at aromatics layer layer N o. treat injected yield 20 0. in extract Mono-methyl ether of ethylene glycoL 21 38 215 0 51. 2 1. 4856 1. 4500 91. 0 Tri-ethanol amine 20 39 312 4. 9 56. 5 l. 4892 1. 4413 94. 2 Tri-methyl phosphate 20 3 340 5.0 57. 2 1.4890 1. 4407 04. 0 216 5. 4 45. 3 1. 4902 1. 4502 95. 1

From the above data it is apparent that these solvents are readily removed from toluene by means of water.

EXAIVIPLE 2 A petroleum naphtha boiling in the range from about 212 F. to 284 F. and consisting of about aromatic materials was solvent extracted using various quantities of mono-methyl ether of (ii-ethylene glycol. Various quantities of water were injected at difierent points 01' the sys- The above data illustrate that when using solvent mixtures of the present invention, it is possible to secure increased yields of higher quality products. EXQMPLE 4 sults of the various operations are summarized as follows:

TABLE 6 Raill- Percent Percent Percent note Extract arofia Treat 32%? oil in extract reirac- "g y matics extract yield tive ind a in index ax extract 1 122. 8 0 10. 0 13. 6 1. 4636 1. 4395 97 2 289- o 0 7. 8 24. 4 l. 4618 1. 4881 85. 5 0 11. 0 10. 5 1. 4658 1. 4899 97 116. 0 5. 1 8. 5 10. 8 1. 4650 l. 4925 100 0 5. 1 8- 3 15. 8 1. 4635 1. 4923 100 199. 0 4. 85 8. 0 17. 0 1. 4624 1. 4920 100 The data from these operations illustrate the Operation No. 1

unexpected desirableresults secured when utilizing diethylene glycol in conjunction with water. 1 000 10101005 11111111110 When using the same percentage of-treat. extract yields are secured consisting of 100% aromatic Vol- Per- Vol- Perv51 Permaterials. This illustrates that it is possible with the solvent mixtures of the present invention to A ti 53 a 53 secure in a single countercurrent operation 100% zx ihafijfiffflgflgi: ,1: 38 2; '13

i extracts. ammat c 100.0 100.0 3 100.0 00.7 100.0

EXAMPLE 5 Operation No. 2

A cracked petroleum distillate boiling in the range from about 200 F. to 400 F. was countercurrently extracted with anhydrous monomethyl v1 P V] P V] P ether of diethylene glycol at 85 F. The feed oil g g; g; cent had a gravity of 50.5 A. P. I. and a refractive index 01 1.4348 at C. and contained about Momma, 53.3 53' 8'8 8M 4 no 40% of aromatics and olefins. Various quantities Parafllns and 11001101101100.-. 40.1 40.1 2.2 20.0 44.5 50.0 of water were injected in the diflerent operations 20 1m 10 0 10M 8 10M and the results may be summarized as follows:

Test: 7

Percent water m1 Extract K ttwi 111 Percent 11mm Gravity, k a G i 111111111100 0 ti nNo. solvent percent A.P. m 1mm I refractive 1.1021 23" mm 123:. .0002. 1m

umn feed inlet Operation N0. 1 EXAMPLE '7 A petroleum fraction containing 20% aromatic Feed Extract 33mm" materials was solvent treated with 100% by volume of dry and aqueous monomethyl ether of ethylene glycol at various temperatures. The mm mm mm mm mt results of these operations are summarized as 40 follows: The results illustrate how the aqueous 1 12.0 12.0 0.2 35.0 0.5 0.0 3%.;{5 2&0 solvent may be used at room temperature while Parafllns and n ph h n M 220 516 refrigeration must be used with the dry solvent.

100.0 100.0 11.1 100.0 a 1000 TABLE 9 Operation No. 2 45 P OWMO- as ass it? :200:

"F oitreat in 100 '10 Feed Extract mmmiic m m 1 -02 0 11 18.2 Vol- Per- Vol- IP01 701- Perume cent 11m cent ume cent. 132 8 23 5 i% g 45 2% 3% .1 ti 12.0 12.0 0.3 30.0 4.5 0.0 0:33;"? 33.0 33.0 9.1 300 21.3 20.0 2 g Parsflins and naphthen 55.0 56.0 5.6 23.0 50.2 66.0 8 +85 23 loo-0 loo-0 WM 55 Similar operations were made on feed petroleum oils containing 50% aromatic materials with the EXAMPLE 6 following results:

TABLI: 10 A Mlrando cracked distillate was countercurrently solvent extracted with anhydrous monoe0 methyl ether of diethylene glycol at F. The Operation No 'fggpg gc e t i' i Percent feed oil had a gravity of 56.8 A. P. I. and a re- 01 1001' 1111:0311 "3231 :53; fractive index of 1.4207 at 20 C. Water was inJected at several stages. The results of the 1 0 56 79 4 various operations are summarized as follows: 65 2 +88 5 53 Teen: 8

Extract Ram o t N Peri Percent Yieldt Ext'rfiot raincgf ate pera ion 0. can we er percen 0. ve

treat injected extract 3? 1.1. index at E2, 338g? These operations demonstrate that in orderto secure the same concentration of aromatics in the extract, it is possible to operate at considerably higher temperatures in accordance with point between the oil feed inlet and the solvent extract phase outlet, separating the phases and removing the solvent therefrom.

2. Process in accordance with claim 1 in which the present invention. 5 the raffinate and the extract are recovered from the solvent by subjecting to treatment with ad- EXAMPLE 8 ditional quantities of water.

Various petroleum fractions were extracted Process in a co da e Wit C a m 1 in Wh ch with monomethyl ether of diethylene glycol using said solvent is selected from the class of monovarious percentages of water. The operation was 10 alkyl ethers of e y E Y S i which t conducted using five stripping stages and two realkyl g p contains not over tWO Carbon atoms flux stages and by injecting water in each stage. n the olecu e.

The inspections on the feed material, the extract, I p ved so e t t e p ocess comprisand the rafiinite of these operations are suming i t o a Petroleum l t 8- 6 11 1 56 marized as follows: 15 current solvent treating system, contacting the TABLE 11 same with a solvent selected from the class of solvents which are characterized by being com- 0 pletely miscible with toluene in the anhydrous 1322 ifl %21? state, very slightly miscible with toluene in the aqueous state and which may be readily removed Inspections Feed Feed from toluene with water, under conditions to g o t 1t,r' 55 21 1 form a solvent poor or raffinate phase and a fi gf 241 26 27 solvent rich or solvent extract phase, introduc- Refluxratio (14111 0.411 11211 ing water into the system at a plurality of stages, separating the raffinate phase and the solvent Ext. Rail. Ext. Rafi. Ext. Rafi.

Yield percent 23.8 76.2 32.0 68.0 34.0 66.0 A.P.I 55.7 49.0 58.0 49.6 58.7 48.2 42.8 51.0 Refractive index at 20 0. 1. 4225 1.4410 1.4167 1. 4376 1.4150 1.4405 1.4601 1. 4302 Bromine number 38 45 36 47 33 26 22 Kattwinkel number 46 57 37 63 46 63 34 35 28 a7 26 20 24 17 22 9 1 26 0 26 :19 17 74.6 57.2 t 74.4 56.2 61.1 74.3 41.5 154 1 188 266 260 275 12.0 1 10.5 9.0 5.0 38.5 93.5 '360 31.0 63.0 60.0 61.0 59.0 90.0 5 78.0 78.0 78.5 2.0 91.5 00.0 90.0 90.0 4.0 30.5 3.0 96.0 95.5 96.0 96.0 36.5 61.0 31.0 67.5 51.5 65.0 86.0 03.5 85.0 356F d0 95.0 97.5 05.0 1 11151 boiling pointF 315 323 325 372 369 974 90% distilled F 254 350 354 345 331 5 Recovery 99.5 98.5 99.5 95.0 98.5 95.0 ss 0.5 0.5 0.5 1.0 0.5 1.0 Residue do 1. 0 1. o 1. 0 1. 0 1. 0 1.0

or w The conditions and methods of operation in accordance with the present invention may be widely varied. The temperatures, solvents and amount of water injected in one or more stages may be adjusted to secure optimum results, depending ups the particular feed material used and the solvent mixture used.

The invention is not to be limited by any theory or mode of operation, but only by the following claims in which it is desired to claim all noveltv insofar as the prior art permits.

inlet and the raffinate phase outlet and at a extract phases, removing solvent from the extract in an initial stage by treating with water, separating the water and removing the solvent therefrom, separating the extract substantially free of solvent and removing the last traces of solvent by countercurrently scrubbing with additional water in a secondary stage, removing solvent-free extract from said secondary stage and said scrubbing water, subjecting said raffinate phase to countercurrent treatment with said scrubbing water in a raifinate solvent separator, removing solvent-free ratlinate from said raffinate solvent separator and said scrubbing water, then introducing said scrubbing water into said initial solvent extract separating stage.

5. Process in accordance with claim 4 in which said solvent is selected from the class of ethylene glycols and the derlvitives of ethylene glycols.

6. Process in accordance with claim 4 in which said solvent is triethanolamine.

7. Process in accordance with claim 4 in which said solvent is triethyl phosphate.

GORDON W. DUNCAN. JAMES M. WHITELEY, JR. 

